How the Doyle estimate works
For diameter D in inches and length L in feet, estimated board feet = (D − 4)² × L ÷ 16. Multiply by the number of identical logs for the total. The displayed estimate is rounded to two decimal places; the calculation uses the unrounded value.
A worked example: a 16-inch diameter, 16-foot log gives (16 − 4)² × 16 ÷ 16 = 144 board feet. Three identical logs give 432 board feet. These numbers illustrate the formula; they are not measured production results.
Measure before you calculate
- Identify the smaller end of the cut log.
- Measure its diameter inside the bark, not the outer bark diameter.
- Enter the log length in feet.
- Group only logs with the same measurements under one quantity. Calculate different sizes separately.
A practical check before using the number
Record the diameter, length, and the word “Doyle” beside every estimate. A number without its named scale is easy to compare incorrectly with a buyer's quote or a mill's tally. Ask the buyer or sawmill which scale and measurement convention they use before comparing totals.
This tool makes the measurement assumptions visible. It does not deduct rot, cracks, sweep, or other defects, and it does not inspect a log. The quantity field repeats the same measurements; it does not average several different logs. For a mixed load, keep separate estimates for each size.
Log scale versus finished boards
The log estimate is a prediction of lumber yield. Once the log has been sawn, measure and tally the individual boards with the board foot calculator. A rectangular-board volume calculation and a log scale answer different questions, so their totals need not match.
Frequently asked questions
Does this calculate a standing tree?
No. The inputs describe a cut log. Standing-tree volume estimates require a different measurement method.
What if my mill uses Scribner or International scale?
This tool only implements Doyle. Do not treat its result as a result under another scale; use the method your buyer or mill specifies.
Why must diameter be greater than four inches?
The formula subtracts four inches before squaring. This tool rejects smaller diameters so squaring a negative number cannot produce a misleading positive estimate.
Will I get exactly this much lumber?
No. The result is an estimate under a named log rule. Defects, sawing choices, and mill equipment affect the actual tally.
Method reference
The Doyle equation is documented in Louisiana's published description of the Doyle log rule. General log-measurement context is available from Mississippi State University Extension. These references identify the method; this tool is not advice about a timber sale or applicable local law.